This invention relates to a plasma monitor for measuring the distribution of particular chemical species such as particular atoms, molecules, ions and the like contained in plasma generated inside an instrument making use of the plasma such as sputtering and dry-etching instruments.
Plasma monitors making use of the light emission of plasma generated inside an instrument have been proposed in the past so as to determine the film deposition rate or the film composition in sputtering or the etching rate or the end point of etching in dry-etching.
In plasma monitors for dry-etching, for example, the light emitted by the material to be etched is taken out from the plasma and the etching rate or the end point of etching is detected by the intensity (related to concentration of species) of the light.
In plasma monitors for sputtering, on the other hand, the light emission of two particular kinds of chemical species is taken out from the plasma generated during sputtering and the film deposition rate or the film composition is detected by the ratio of these chemical species.
In the conventional plasma monitors of the kinds described above, however, the light emission of the plasma generated inside the instruments is collected as a whole and hence, the plasma condition is grasped only in the gross.
In other words, the plasma monitors of the prior art fail to grasp the variance of the conditions of deposition or etching inside the instrument because they can not measure the distribution of the concentration of chemical species contained in the plasma generated inside the instrument. For this reason, data necessary for controlling suitably the conditions of etching or sputtering can not be obtained even though excessive or insufficient etching is likely to occur in the case of dry-etching or variance occurs in the thickness of the deposited film or in the film composition in the case of sputtering.